Compact, high-efficiency, gas/liquid separator method and apparatus

Abstract

A method and apparatus for separating a wellhead fluid mixture containing oil and gas phases obtained from hydrocarbon production systems into its constituent parts employs a pressure vessel having an inlet for entry of the wellhead fluids mixture and an outlet for exit of a separated gas referred to as export gas. A primary centrifugal separator is provided in the pressure vessel for centrifugally separating a first portion of the oil from the wellhead fluids mixture to produce a wet gas containing some remaining oil. A second centrifugal separator is also provided in the vessel and performs a second centrifugal separation operation on the wet gas to remove substantially all of the remaining oil from the wet gas to produce the export gas which is conveyed out of the pressure vessel. The oil and remaining oil separated from the wellhead fluids mixture is conveyed from the pressure vessel via another outlet.

We claim:  
     
       1. An apparatus for separating an oil/liquid phase from a gas phase contained in a wellhead fluid from a hydrocarbon production system, comprising, in combination with the hydrocarbon production system: 
       a vessel having a wellhead fluid inlet connected to the hydrocarbon production system, for entry of wellhead fluid, a gas export outlet for exit of export gas separated from the wellhead fluid, and an oil/liquid export outlet for exit of oil/liquid separated from the wellhead fluid;  
       means in the vessel defining a main oil/liquid inventory compartment at a lower end of the vessel, the oil/liquid export outlet communicating with the inventory compartment, a secondary compartment at an upper end of the vessel, and means for connecting the inventory and secondary compartments to each other;  
       a primary centrifugal separator in the vessel for separating a majority of the oil/liquid phase from the wellhead fluid to leave a wet gas phase, the primary centrifugal separator comprising a riser tube with an open lower end communicating with the wellhead fluid inlet for receiving upwardly flowing wellhead fluid, the riser tube having a closed upper end, a plurality of curved-arms spaced around the riser tube for causing a majority of the oil/liquid phase to separate from the wellhead fluid to leave the wet gas phase, each curved-arm having an axially extending curved wall, curving away from the riser tube between a root edge of the curved wall at the riser tube and an outer edge of the curved wall spaced outwardly from the riser tube, at least one radial partition in the curved-arm, for dividing an inner space defined by the curved-arm into multiple levels, the primary centrifugal separator also comprising a return cylinder around the riser tube and curved-arms, for receiving oil/liquid phase moving outwardly by centrifugal force from the outer edge of the curved-arms, the return cylinder having an open lower end extending into the inventory compartment for carrying the oil/liquid phase downwardly to the inventory compartment, the return cylinder having an open upper end for passing the wet gas phase; and  
       a secondary centrifugal separator in the vessel spaced above and axially aligned with the primary centrifugal separator by an open interstage region, the secondary centrifugal separator receiving the wet gas phase and comprising a plurality of tangential inlet vanes into which the wet gas phase passes for further separating oil/liquid from the wet gas phase to leave a dry gas phase, the secondary centrifugal separator including skimmer means defining skimmer slots above the inlet vanes for receiving the dry gas phase and for channelling the further separated oil/liquid downwardly into the secondary compartment, the further separated oil/liquid passing from the secondary compartment to the inventory compartment through the means for connecting the inventory and secondary compartments, the skimmer means having an open upper end communicating with the gas export outlet for passing the dry gas phase to the gas export outlet.  
     
     
       2. An apparatus according to  claim 1  wherein the return cylinder includes a plurality of perforations therearound, above the riser tube. 
     
     
       3. An apparatus according to  claim 2  wherein the open upper end of the return cylinder has a radially inwardly extending lip, the open upper end of the skimmer means also having a radially inwardly extending lip. 
     
     
       4. An apparatus according to  claim 3  including a lower support plate extending across the vessel between the inlet vanes and the skimmer means, the support plate defining a lower boundary of the secondary compartment, the means for connecting the inventory and secondary compartments comprising a tube opening into the support plate and extending to the inventory compartment. 
     
     
       5. An apparatus according to  claim 4  including a top plate spaced above the support plate and extending across the vessel above the skimmer means, the open upper end of the skimmer means extending through the top plate and at least one hole in the top plate for receiving any separated oil/liquid passing above the top plate, through the top plate for return to the inventory compartment. 
     
     
       6. An apparatus according to  claim 5  wherein the oil/liquid export outlet extends through a side of the vessel at a lower end of the vessel which communicates with the main oil/liquid inventory compartment. 
     
     
       7. An apparatus according to  claim 6  wherein a portion of the return cylinder which carries the perforations above the riser tube, is approximately 15-18 inches high. 
     
     
       8. An apparatus according to  claim 7  wherein a distance between an upper end of the skimmer means and a lower end of the curved-arms, is approximately 4 feet.